In downlink transmission of a Long Term Evolution (LTE for short) communication system, a base station such as an eNB (evolved NodeB) transmits a PDSCH (physical downlink shared channel) and a corresponding PDCCH (physical downlink control channel) to each scheduled user equipment according to a scheduling result.
The PDSCH carries data transmitted by the eNB to the scheduled user equipment, and the PDCCH carries scheduling information of the PDSCH corresponding to the PDCCH. The scheduling information is primarily used to indicate transmission format information of the PDSCH corresponding to PDCCH. The PDCCH and the PDSCH are multiplexed in a subframe in a time division manner. The PDCCH is transmitted in the first several OFDM (orthogonal frequency division multiplexing) symbols of the subframe, and the remaining OFDM symbols are used to transmit the PDSCH. In a subframe, the PDCCH of all scheduled user equipments is multiplexed together, and then are transmitted in a PDCCH region; and the PDSCH is transmitted in a PDSCH region, where both the PDCCH and the PDSCH have a specific time domain and a specific frequency domain. The PDCCH region refers to a region occupied by the PDCCH in the time domain and the frequency domain, and the PDSCH region is a region occupied by the PDSCH in the time domain and the frequency domain.
In further evolution of the LTE system, MU-MIMO (multi-user multi-input multi-output) and CoMP (coordinated multi-point transmission) need to be supported to improve system performance, and other similar technologies need to be applied. As a result of such technologies, the number of user equipments that need to be scheduled simultaneously increases. However, the capacity of a PDCCH is limited, which restricts the number of user equipments that can be scheduled in one subframe. Therefore, the prior art enhances the PDCCH, and a part of resources of the original PDSCH region is allocated for transmitting the enhanced PDCCH, that is, an E-PDCCH (Enhanced-Physical Downlink Control Channel). In this way, the capacity of the PDCCH control channel is improved, that is, the number of user equipments scheduled simultaneously is increased, where the E-PDCCH is formed by E-CCEs (enhanced control channel element).
However, in an LTE system, a resource unit for carrying an E-PDCCH is an RB pair (resource block pair). Each RB pair occupies 12 subcarriers in the frequency domain, and occupies one subframe, that is, two slots in the time domain. However, resources available to the E-PDCCH are a set of REs (resource element) except the PDCCH region and what is occupied by various RSs (reference signal) in each RB pair, where each RB pair can carry multiple E-CCEs. Because various RSs are distributed unevenly in the RB pair, the number of resources occupied by each E-CCE may differ or vary significantly, and the performance of the E-CCEs is imbalanced, which affects E-CCE scheduling or receiving performance.